We were
discussing the various types of notches and weirs i.e. classifications of
notches and weirs and also the difference between Notches and Weirs in the
subject of fluid mechanics in our recent posts.

Now we will go ahead to find out the discharge over a rectangular notch or weir, in the subject of fluid mechanics, with the help of this post.

We must note it here that the expression of the discharge over a rectangular notch or over a weir will be same.

Now, let us consider that we have channel carrying water and let us think a rectangular notch or weir with this channel as displayed here in following figure.

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Now we will go ahead to find out the discharge over a rectangular notch or weir, in the subject of fluid mechanics, with the help of this post.

We must note it here that the expression of the discharge over a rectangular notch or over a weir will be same.

Now, let us consider that we have channel carrying water and let us think a rectangular notch or weir with this channel as displayed here in following figure.

We have
following data from above figure and these data are as mentioned here.

H = Head
of water over the crest

L = Length
of the rectangular notch or weir

Let us
consider one elementary horizontal strip of water of thickness dh and length L
as displayed in above figure.

dh =
Thickness of elementary horizontal strip of water flowing over the rectangular
notch or weir

h = Depth
of elementary horizontal strip of water flowing over the rectangular notch or
weir

C

_{d}= Co-efficient of discharge
Area of elementary
horizontal strip of water = L x dh

We will determine
the value of discharge dQ through the elementary horizontal strip of water. After
securing the expression for discharge through the elementary horizontal strip,
we will integrate the expression between the limit 0 to H and we will have the
expression for the discharge over a rectangular notch or weir.

Now we
will go ahead to start a new topic in the subject of fluid mechanics i.e. Discharge over triangular notch or weir with the help of our next post.

Do you have any suggestions? Please write in comment box.

Do you have any suggestions? Please write in comment box.

**Reference:**

Fluid
mechanics, By R. K. Bansal

Image
Courtesy: Google